Various selective excitation methods have already been developed. One method disclosed by Patent Disclosure No. Showa 60(1985)-185149 sets the selective excitation pulse sequence in two directions (x and y) as shown in FIG. 6. In other words, positional selection gradient magnetic field G.sub.x is applied in the first direction or direction x (slice axis) for example. Then a selective excitation of spin is effected by applying a RF pulse 90.degree. to the first direction (90.degree. excitation RF signal). Then after applying a spin warp in the second direction specified in an area that orthogonally intersects the first direction or in direction y (warp axis) for example, and applying positional selection gradient magnetic field G.sub.y, a selective inversion of spin is effected by applying an RF pulse 180.degree. in the second direction (180.degree. excitation RF signal). Then a spin echo signal is received by applying readout gradient magnetic field G.sub.z in the third direction that orthogonally intersects the first and second directions, respectively, or direction z (read axis). As a result, a spin echo signal in an area of delta x in thickness and delta y (width) in both directions (x and y) can be obtained.
There are methods for generating NMR signals other than that mentioned above. For example, there is a method by which a spin echo signal is generated by inverting a gradient magnetic field after exciting it by applying a 90.degree. RF pulse. There is another method by which a Free Induction Decay (FID) signal (generated immediately after 90.degree. RF pulse excitation) is used as the NMR signal. Because these methods use a 90.degree. RF pulse instead of a 180.degree. RF pulse for excitation, a selective excitation method using both types of excitation signals (90.degree. and 180.degree. RF pulse signals) in both directions (x and y) cannot be adopted. If selective excitation cannot be effected in two directions, a turn is made in the directions where there is no selectivity, and aliasing artifacts are created as shown in FIG. 7 if a measured NMR signal is used as a raw data for reconfiguring an image under Fourier transformation.